The present invention relates generally to a method and apparatus for forming and shaping metal, plastic, paper, fiberboard, paperboard, or the like, sheets or webs in the assembly and construction of a novel product, consisting of or comprising an expanded triangularly celled structure useful per se as a packing material or, when combined with one or more face sheets, useful in the makeup of packages and containers for enclosing articles of commerce, or useful as rigid structural panels in the assembly of various structures, or in the construction of buildings or manufacture of vehicles or parts thereof.
At present, one generally accepted method of joining flat webs of, e.g., paperboard or fiberboard material, to produce a panel product having a thickness dimension greater than that of the material employed in its makeup, is the assembly of so-called corrugated board stock fabricated, for example, from coarse fiber kraft material referred to in the trade as liner board, and a center medium material. This known product comprises a laminate of two outer liner sheets bounding a fluted center medium member which is corrugated by passage through meshing or gear-like cylinders with subsequent "take-up" of some 50% of the length of the medium in the formation of convolutions therein. Adhesive is applied to the apex of each convolution of the center medium to attach the planar outer sheets thereto thus producing a panel configuration. This known product exhibits rigidity in a direction parallel to the corrugations or convolutions and is generally weak in a direction at right angles to these convolutions.
There is a broad similarity between the present invention and the production of such corrugated board stock in that the present invention also contemplates that two outer liner sheets can be attached to opposite sides of a center medium sheet after the center sheet has passed between forming cylinders. In the present invention, however, the center medium is not corrugated and, instead, is shaped by special forming cylinders to define an array of triangular, alternately displaced forms, the planes of the triangles serving to provide areas for adhesive attachment of the center medium to the outer liner sheets, and the sides of each triangle being folded generally perpendicular to the planes of the liner sheets, thus providing a displacement, or spacing, between the alternate triangular forms so that their planes alternately face opposite sides of the center medium.
Like corrugated media, the preparation of the center medium employed in the present invention is accomplished by use of gear-like forming cylinders but the cylinder peripheries are provided with dual-opposed helical tooth arrangements each of which is broken into a series of triangular elements engaging complementarily shaped recesses in the opposite cylinder. Unlike the known corrugating procedure, the method and apparatus of the present effects intermittent cutting of the web being formed in a plurality of parallel lines oriented longitudinal to the web direction. The cuts are displaced from line to line, thus permitting folding of the triangular sides of each element without lateral take-up in the web. The take-up is entirely in the longitudinal direction of web extension or travel.
A second known method for joining flat sheets employs a cellular configuration between sheets fabricated by a variety of procedures to form so-called "honeycomb" shapes, the side planes of which are perpendicular to said sheets. The "honeycomb" edges are attached to the boundary sheets by bonding means. The product of the present invention is also broadly similar to honeycomb in that the triangular side fold of each element or cell provides ribs which are generally perpendicular to the outer sheet, panel or web, to form cellular enclosures. However, unlike honeycomb, the base line of each triangular form in the present invention is cut, to relieve the web laterally and to provide one open side, thus permitting the passage of gas or fluid through and between these cellular members throughout the structure. Moreover, unlike honeycomb, the forming apparatus and process of the present invention permits high speed forming and assembly of the novel product of the present invention in virtually all materials, employing bonding or mechanical means for connection of the formed center medium to one or more outer boundary sheets.
The principal industrial advantage of the present invention lies in the simplicity of the process with which the product is achieved. A combination of web handling apparatus may be employed, for example, in which three webs pass from unwind rolls through draw rolls or delivery apparatus with one web passing through the nip of a pair of forming cylinders having the dual opposed helical-triangular forms described earlier, operative to cut and fold the web constituting the center member of the final product, followed by passage of the formed web to adhesive applicators which apply adhesive to the flat triangular planes formed on each side of the formed mechanism, followed by laminating steps introducing two planar outer webs to opposite sides of the center member with required heating or cooling to bond or set the adhesive agent used.
The novel forming cylinders used in the present invention can be mounted in existing corrugated machinery in place of the conventional corrugating cylinders customarily used in such machinery. Operational speeds of the resulting equipment are better than those of existing corrugating equipment however, because of the larger areas afforded for connection of the outer liner sheets to the center medium. Moreover, unlike conventional corrugating apparatus, the forming cylinders of the present invention permit repair without need for replacement of an entire cylinder or even demounting the cylinder for this purpose.
It has been found that the cutting and folding procedures employed in the present invention exhibit substantial improvements over techniques utilized heretofore in conjunction with distensible materials that are formed by application of heat and/or pressure. Such distensible materials lend themselves to embossing, vacuum forming, and other procedures involved in the cutting of a web, e.g. like those described in Koski U.S. Pat. No. 3,703,432 issued Nov. 21, 1972, where embossing and cutting wheels or cylinders are utilized which depend upon the utilization of heat, and which effect a change of gauge in the material since the formed shape is created by drawing material from the adjoining areas.
In the production of the formed panel of the present invention, the gauge of the material is maintained substantially constant since the material is merely folded, and since the folds are accommodated in such a way that a uniform take-up occurs only in the longitudinal direction of the web. To achieve such folding, a triangular form must be employed in which the sides extend along straight lines. Similarly, the several triangular forms must be identical and must dispose base lines oppositely and alternately to gather the web uniformly across the web width. In addition, the cutting and folding procedures employed in the present invention minimize the space or intervals between the base line cuts. The space between adjacent cuts should be approximately one-twelfth the length of a given cut and preferably never more than 15% or less than 5% of said length. The radius of the nose or apex of the triangular form in the plane, as well as in the perpendicular relationship, must have a diameter equivalent to this spacing. With such proportioning, the hazard of puncturing the web or causing it to distort objectionably is substantially reduced. The end result is quite different from that effected in the aforementioned Koski patent since the triangular form contemplated therein is not self-accommodating, and folding of the Koski triangular form, even with the cut relief in the sheet, is not possible without deforming, distending or stretching the material. In the present invention, the cuts employed open the sheet and make possible the gathering of the material by the accommodation of the folding in alternating planes so that the thickness of the combination thus achieved is a function of the shared fold dimension of each triangle side.
The base line cuts in the present invention can be other than a straight line without disturbing the folding characteristics of the folded side of the triangular shape, or its formation. A curved cut, or one of U-shape can, if desired, be employed, e.g., as an auxiliary means for connecting cover sheets or webs to the folded center panel.
It is accordingly an object of this invention to produce a board or panel having a central medium of novel configuration exhibiting isotropic rigidity and strength, with respect to its plane.
It is a further object to provide such a novel medium or panel having a configuration adapted to receive additions of reinforcement within the openings of the medium for the purpose of enhancing column strength and improving the flat crush properties of the medium.
It is also an object to provide a novel panel having a center medium which is reinforced by discs or washers enclosed within the confines of the dual triangular cells of the novel medium, to improve column strength and the flat crush properties of the overall panel.
It is also an object of this invention to provide an apparatus and process capable of achieving high speed production of board or panels of novel configuration fabricated from any of a variety of materials and in any of various different gauges, all by employing generally the same machine configuration.
It is a further object to apply the process of the present invention in conjunction with known spiral winding techniques, in the production of individual packaging forms such as tubs, buckets, barrels and rectangular and square configurations fabricated of a novel medium.
Another object of this invention is the provision of a technique which, through the introduction of process variations achieves a variation in the triangular cell form size of the novel medium with respect to lateral web direction, to produce web crescents or arc forms adaptable to the making of tapered tubs, buckets, cups and other nested configurations.
It is another object to provide a novel forming apparatus capable of axial adjustment in a longitudinal direction of one or both cylinders employed in the invention, so that the triangular base line of each tooth component engages its adjoining member in controlled shear relationship to that member. A related object is to provide an apparatus wherein the shear adjustment is openable to provide for displacement of material rather than cutting thereof when a web of flexible plastic material is being formed, thereby to cause the material to flow under pressure so as to provide a membrane, or a closed cell form in the formed medium.
It is a further object of this invention to employ various side fold dimensions of the triangular components of the formed center member so a variation is spacing between panels and a variety of widths or gauges can be achieved without changing the center spacing of the triangular forms utilized.
It is another object of this invention to provide added strength in the combination by reducing the number of triangular components per unit area in said center panel, or, conversely, to increase the gauge substantially by enlarging the size and decreasing the number of triangular components provided per unit area.
A further object of this invention is to provide an apparatus that simultaneously cuts and folds a component in the plane of the web as it passes between two forming cylinders, thus permitting a gathering or take-up of the web in its longitudinal direction, while providing relief in the lateral direction, thus accomplishing diagonal and generally perpendicular folds which are alternately placed in relation to the direction of web travel.
It is another object of this invention to control the interval or spacing between longitudinal cuts in the novel medium, to permit expansion of the sheet by a folding of the triangular forms produced without tearing or overtly distorting the uncut areas of the sheet. A further object is to use contoured surfaces on the periphery of forming cylinders which are arranged to cut and fold a web in novel fashion thereby to produce lateral variations in gauge in a given web as it passes through the forming cylinders.
It is a further object of this invention to produce a novel product that lends itself to connection by overlapping and the telescoping of triangular forms within one another to produce a seam in a cylindrical product fabricated from the formed medium of the present invention.
It is a further object to be able to produce a cylindrical product, fabricated from the formed medium of the present invention, which will wind on a 45.degree. mandrel, as in spiral winding, or which will wind, as is normal, in line with the longitudinal direction of web travel.
It is a further object of this invention to provide a novel process and product wherein a web is provided with parallel cuts longitudinally of the web, and wherein the web material is folded along the cuts while alternating the fold direction, to produce a series of angular trusslike forms in which the longitudinal apexes of the resultant forms connect the formed members to the planes of one or more outer panels associated therewith.